The present invention relates to a method of forming a film on a substrate and an apparatus thereof.
In a photolithography process in the semiconductor device fabrication processes, for example, resist coating treatment in which a resist solution is applied to the surface of a wafer to form a resist film, exposure processing in which the wafer is exposed in a pattern, developing treatment in which development is performed for the exposed wafer, and the like are performed to form a predetermined circuit pattern on the wafer.
At present, in the above-described resist coating treatment, a spin coating method is in the mainstream as a method of applying the resist solution. According to the spin coating method, the resist solution is discharged to the center of the wafer and the wafer is rotated. This allows the resist solution applied on the wafer to spread by centrifugal force, whereby a uniform resist film can be formed over the entire face of the wafer.
However, in the spin coating method, since the wafer is rotated at high speed, a large amount of resist solution scatters from the peripheral portion of the wafer, resulting in a big waste of resist solution. Further, the apparatus is contaminated by the scatter of the resist solution, bringing about harmful effects such as a need for cleaning frequently.
Hence, instead of the spin coating method in which the wafer is rotated, a method, in which a nozzle for discharging the resist solution and the wafer move relative to each other to apply the resist solution, for example, evenly on the wafer in lattice form, is conceivable.
However, in the case in which the resist solution is applied in the manner of the so-called single stroke, it is feared that the resist solution applied at the peripheral portion of the wafer protrudes by surface tension, with the result that a resist film is not uniformly formed. When exposure is performed with the resist film protruding at the peripheral portion, the peripheral portion becomes a defective portion which can not be used as products, whereby yields correspondingly decrease.